Severe hypoplastic crisis among patients with sickle cell anemia has been associated with infection with what appears to be a non-cultivatable parvovirus-like agent. Immune adherence hemagglutination and radioimmunoassay techniques have been adapted to identification of this agent and its antibody: approximately 60 percent of normal populations have been found to be antibody-positive. Attempts to transmit the serum parvovirus-like agent to primates are in progress. Attempts to demonstrate replication in tissue culture have been partially successful.